KBTV issues Area Forecast Discussion (AFD) valid 2019-12-11T05:48:00Z 912 FXUS61 KBTV 110548 CCA AFDBTV Area Forecast Discussion...CORRECTED National Weather Service Burlington VT 1248 AM EST Wed Dec 11 2019 .SYNOPSIS... A cold front crossing the North Country this evening will result in rapidly falling temperatures. As temperatures plummet below freezing, any standing water or slush will rapidly freeze, and a few icy spots are possible tonight and into the morning commute on Wednesday. High temperatures on Wednesday will generally be in the 20s to near 30. Another trough approaching from the Great Lakes will bring the potential for additional snow showers during Wednesday afternoon. The next chance for widespread precipitation will occur Saturday, with moderate rain generally expected across the North Country. && .NEAR TERM /THROUGH TONIGHT/... As of 939 PM EST Tuesday...A narrow band of light snow has persisted across the region, extending from southern Franklin County, NY across portions of Chittenden, Lamoille, and Washington Counties in VT. There's not much accumulation with this activity, maybe a tenth of an inch or two, and it should gradually wane through the early morning hours. This band is likely associated with a dewpoint boundary, behind which is much drier air. This should help limit black ice potential for far northern VT/NY, but still expect there could be patchy slick spots for southern and south central VT where moisture lingers and temperatures are at or just above freezing. Best chances for any black ice would be on untreated and secondary roads. Have just made adjustments to the forecast to match the latest radar trends, otherwise things are in good shape. Previous Discussion...Slow-moving deep-layer frontal zone continues to bring light rain across central/s-central VT this afternoon. A shallow/secondary cold front shifting into the St. Lawrence Valley will sweep eastward this evening. This secondary front will come through generally dry, but strong low-level CAA is expected, along with a W-NW wind shift. Briefly gusty winds of 20-30 mph are possible through this evening with good low- level mixing. As temperatures fall, the main concern is a rapid refreeze of any slush or standing water from today's snowmelt. Some surfaces will sufficiently dry out first, but patchy black ice may occur on untreated surfaces that are initially wet through this evening. Have issued a Special Weather Statement to address for this evening into the overnight hours. Temperatures by daybreak expected to fall into the teens, except locally in the lower 20s across the valleys of s-central VT. On Wednesday, narrow surface ridge axis brings dry/partly sunny conditions during the morning hours. This ridge axis shifts out quickly as next shortwave approaches from the Great Lakes region. Flow quickly shifts back swly by afternoon, and lake enhanced snow showers will begin developing across St. Lawrence and Franklin counties by 18Z. Have a period of 70-80 PoPs across the Adirondacks mid-late afternoon, with chances for late afternoon and evening snow showers elsewhere as trough axis shifts across the region. Snow accumulations of 1-3" are possible from swrn St. Lawrence County into the Adirondacks, with generally an inch or less elsewhere across the North Country. Wednesday's highs generally 25-30F. Wednesday night will feature brisk conditions early, with NWLY gusts 25-35 mph possible in the wake of the surface trough passage. Clearing skies and diminishing winds after midnight should allow temperatures to fall into the low-mid teens, except locally in the single digits across the Adirondacks and far nern VT. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... As of 329 PM EST Tuesday...No real changes for Thursday through Friday night with high pressure in control of the sensible weather across the North Country. Below normal temperatures are expected on Thursday as Canadian high briefly settles in. Breezy winds Thursday morning will diminish towards afternoon and although it'll be chilly, a dry airmass will be in place allowing for plenty of sunshine during the day. High temperatures should generally be around 20 for the Northeast Kingdom and higher terrain of the Adirondack and Green Mountains, and low to mid 20s elsewhere. High pressure will begin to slide eastward Thursday night as winds aloft turn out of the southwest ahead of our next approaching system for Saturday. Temperatures on Friday will moderate to near seasonable norms in the low to mid 30s. Despite warming temperatures it will still feel chilly Friday as southerly winds increase around 10-15 knots with gusts upwards of 20 knots at times during the afternoon. Warm air advection will continue overnight Friday with low temperatures generally remaining steady in the low to mid 30s. && .LONG TERM /SATURDAY THROUGH TUESDAY/... As of 329 PM EST Tuesday...The main story for the extended will be the "nor'easter" for Saturday. Overall, model guidance is in relatively good agreement on the evolution of this system however there are some differences on upper level structure and placement of the surface low with slight variations on the timing/placement of phasing shortwaves aloft. There is still plenty of time to hammer out the details on this system, especially in regard to placement of heaviest QPF. One thing of note, while highest PWATs remain well to our south and east, sounding climatology for ALY at 12z Dec 14 show PWATs around 1" near the daily maximums for the day. Currently, guidance indicates around 0.75" across northern New York and northwestern Vermont with amounts increasing to around 1.50" across southeastern Vermont. Unfortunately, one trend which has been covered well by all guidance is the likelihood that this event will be primarily rain, expect for maybe the highest peaks. At this time, have run with rain/snow based on surface temperatures due to strength of warm nose aloft, however there is the potential for pockets of freezing rain for the deeper hollows across eastern Vermont and the Connecticut River Valley at the onset of precipitation early Saturday morning. Soundings indicate the best potential at typical location such as Springfield & St. Johnsbury. Additionally, we will be watching the potential for gusty east-southeasterly downsloping winds late Saturday morning as soundings indicate 40-45 knot low level jet developing around 925- 900 mb. Soundings indicate a stable layer in place as this coincides with precipitation, but given dry slot development across this location Saturday afternoon a few locations could see brief gusts up to 30 kt. Colder air finally works its way in the region Sunday afternoon with some lingering snow showers. The pattern for active weather continues with another deepening system developing across the Central Plains poised to impact the region by early next week with uncertainty regarding where the low will track. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/... Through 06Z Thursday...Mainly VFR conditions through the remainder of the early morning hours, with perhaps occasional MVFR in light snow at KSLK, KRUT, and KMPV. Otherwise, dry conditions expected through 18z Wednesday. Snow showers are expected to develop over northern New York and western Vermont after 18z and this could result in MVFR/local IFR visibilities. Otherwise looking at VFR visibilities for much of the period. Northwest winds will persist through Wednesday morning, mainly 5-10 kt. Eventually the winds will turn back to the south and southwest after 14z with most locations seeing winds under 10 knots, but there could be gusts as high as 20 knots late in the period. Outlook... Wednesday Night: VFR. Windy with gusts to 30 kt. Chance SHSN. Thursday: VFR. NO SIG WX. Thursday Night: VFR. NO SIG WX. Friday: Mainly VFR, with local MVFR possible. Slight chance RA, Slight chance SN. Friday Night: MVFR/IFR conditions possible. Likely RA, Chance SN. Saturday: Mainly IFR, with areas MVFR possible. Definite RA. Saturday Night: Mainly IFR, with areas MVFR possible. Likely RA. Sunday: Mainly MVFR, with local IFR possible. Likely SHRA, Likely SHSN. && .MARINE... A Lake Wind Advisory continues into tonight. A cold front crossing the North Country will maintain good low-level mixing, with westerly winds 20-30 kts for a time this evening. Should see winds trend downward to 10-15 kts after midnight. Waves initially 2 to 4 feet should subside to 1 to 2 feet after midnight. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Banacos NEAR TERM...Banacos/Hastings SHORT TERM...LaRocca LONG TERM...LaRocca AVIATION...Evenson/Hastings MARINE...Hastings